IACS Guidelines for Surveys, Assessment and Repair of Hull Structure Bulk Carriers

Transcription

1 No.76 No.76 (1994) (Rev.1 July (cont) 2001) (Rev.2 June 2004) (Corr.1 Sept 2007) IACS Guidelines for Surveys, Assessment and Repair of Hull Structure Bulk Carriers Page 1 of 1 IACS Rec. 2004/Corr

2 IACS INTERNATIONAL ASSOCIATION OF CLASSIFICATION SOCIETIES BULK CARRIERS Guidelines for Surveys, Assessment and Repair of Hull Structure

3 Copyright IACS - the International Association of Classification Societies and the International Association of Classification Societies Limited. All rights reserved. Except as permitted under current English legislation no part of this work may be photocopied, stored in a retrieval system, published, performed in public, adapted, broadcast, transmitted, recorded or reproduced in any form or by means, without prior permission of the copyright owner. Where IACS has granted written permission for any part of this publication to be quoted such quotation must include acknowledgement to IACS. Enquiries should be addressed to the Permanent Secretary: International Association of Classification Societies Ltd, 5 Old Queen Street London, SW1H 9JA Telephone: Fax: Permsec@iacs.org.uk With regard to information published on this website and where the copyright resides with IACS and IACS Ltd., permission is hereby granted for use, as above. Terms and Conditions The International Association of Classification Societies (IACS), its Member Societies and IACS Ltd. and their directors, officers, members, employees and agents (on behalf of whom this notice is issued) shall be under no liability or responsibility in contract or negligence or otherwise howsoever to any person in respect of any information or advice expressly or impliedly given in this document, or in respect of any inaccuracy herein or omission herefrom or in respect of any act or omission which has caused or contributed to this document being issued with the information or advice it contains (if any). Without derogating from the generality of the foregoing, neither the International Association of Classification Societies (IACS) nor IACS Ltd. nor its Member Societies nor their directors, officers, members, employees or agents shall be liable in contract or negligence or otherwise howsoever for any direct, indirect or consequential loss to any person caused by or arising from any information, advice, inaccuracy or omission given or contained herein or any act or omission causing or contributing to any such information, advice, inaccuracy or omission given or contained herein. Any dispute concerning the provision of material herein is subject to the exclusive jurisdiction of the English courts and will be governed by English Law.

4 BULK CARRIERS: GUIDELINES FOR SURVEY, ASSESSMENT AND REPAIR OF HULL STRUCTURE CONTENTS Contents 1 Introduction 2 Class survey requirements 2.1 General 2.2 Annual Surveys 2.3 Intermediate Surveys 2.4 Special Surveys 2.5 Bottom surveys 2.6 Damage and repair surveys 3 Technical background for surveys 3.1 General 3.2 Definitions 3.3 Structural damages and deterioration 3.4 Structural detail failures and repairs 3.5 IACS Early Warning Scheme (EWS) for reporting of significant damage 4 Survey planning, preparation and execution 4.1 General 4.2 Survey Programme 4.3 Principles for Planning Document 4.4 Conditions for survey 4.5 Access arrangement and safety 4.6 Personal equipment 4.7 Thickness measurement and fracture detection 4.8 Survey at sea or at anchorage 4.9 Documentation on board 5 Structural detail failures and repairs 5.1 General 5.2 Catalogue of structural detail failures and repairs Part 1 Cargo hold region Area 1 Deck structure Area 2 Topside tank structure Area 3 Side structure Area 4 Transverse bulkheads including stool structure Area 5 Double bottom including hopper tank structure Part 2 Fore and aft end regions Area 1 Fore end structure Area 2 Aft end structure Area 3 Stern frame, rudder arrangement and propeller shaft support INTERNATIONAL ASSOCIATION OF CLASSIFICATION SOCIETIES CONTENTS 1

5 BULK CARRIERS: GUIDELINES FOR SURVEY, ASSESSMENT AND REPAIR OF HULL STRUCTURE CONTENTS Part 3 Machinery and accommodation spaces Area 1 Engine room structure Area 2 Accommodation structure INTERNATIONAL ASSOCIATION OF CLASSIFICATION SOCIETIES CONTENTS 2

6 BULK CARRIERS: GUIDELINES FOR SURVEY, ASSESSMENT AND REPAIR OF HULL STRUCTURE 1 INTRODUCTION 1 Introduction The International Association of Classification Societies (IACS) is introducing a series of manuals with the intention of giving guidelines to assist the surveyors of IACS Member Societies, and other interested parties involved in the survey, assessment and repair of hull structures for certain ship types. This manual gives guidelines for a bulk carrier type ship which is constructed with a single deck, single skin, double bottom, hopper side tanks and topside tanks in cargo spaces, and is intended primarily to carry dry cargo, including ore, in bulk. Figure 1 shows the general view of a typical single skin bulk carrier with 9 cargo holds. Figure 1 General view of a typical single skin bulk carrier The guidelines focus on the IACS Member Societies survey procedures but may also be useful in connection with inspection/examination schemes of other regulatory bodies, owners and operators. The manual includes a review of survey preparation guidelines, which cover the safety aspects related to the performance of the survey, the necessary access facilities, and the preparation necessary before the surveys can be carried out. The survey guidelines encompass the different main structural areas of the hull where damages have been recorded, focusing on the main features of the structural items of each area. An important feature of the manual is the inclusion of the section which illustrates examples of structural deterioration and damages related to each structural area and gives what to look for, possible cause, and recommended repair methods, when considered appropriate. The IACS Early Warning Scheme (EWS), with the emphasis on the proper reporting of significant hull damages by the respective Classification Societies, will enable the analysis of problems as they arise, including revisions of these Guidelines. This manual has been developed using the best information currently available. It is intended only as guidance in support of the sound judgment of INTERNATIONAL ASSOCIATION OF CLASSIFICATION SOCIETIES 1 1 INTRODUCTION

7 BULK CARRIERS: GUIDELINES FOR SURVEY, ASSESSMENT AND REPAIR OF HULL STRUCTURE 1 INTRODUCTION surveyors, and is to be used at the surveyors' discretion. It is recognized that alternative and satisfactory methods are already applied by surveyors. Should there be any doubt with regard to interpretation or validity in connection with particular applications, clarification should be obtained from the Classification Society concerned. Figure 2 shows a typical cargo hold structural arrangement in way of cargo hold region. Topside tank Upper stool Side shell frames and end brackets Transverse bulkhead Lower stool Hopper tank Double bottom tank Girder Floor Watertight bulkhead Figure 2 Typical cargo hold configuration for a single skin bulk carrier INTERNATIONAL ASSOCIATION OF CLASSIFICATION SOCIETIES 2 1 INTRODUCTION

8 BULK CARRIERS: GUIDELINES FOR SURVEY, ASSESSMENT AND REPAIR OF HULL STRUCTURE 2 CLASS SURVEY REQUIREMENTS 2 Class survey requirements 2.1 General The programme of periodical surveys is of prime importance as a means for assessment of the structural condition of the hull, in particular, the structure of cargo holds and adjacent tanks. The programme consists of Special (or Renewal) Surveys carried out at five-year interval with Annual and Intermediate Surveys carried out in between Special Surveys Since 1991, it has been a requirement for new bulk carriers to apply a protective coating to the structure in water ballast tanks which form part of the hull boundary, and, since 1993, to part of the side shell and transverse watertight bulkheads structures in way of the cargo holds The International Maritime Organization (IMO), in 1997 SOLAS Conference, adopted structural survivability standards for new and existing bulk carriers carrying the high density cargoes. All new single side skin bulk carriers, defined as ships built on or after 1 st July 1999, are required to have sufficient strength to withstand the flooding of any one cargo hold taking dynamic effects into account. All existing single side skin bulk carriers, defined as ships built before 1 July 1999, must comply with the relevant IACS criteria for assessing the vertically corrugated transverse watertight bulkhead between the first two cargo holds and the double bottom in way of the first cargo hold with the first cargo hold assumed flooded. The relevant IMO adopted standards, IACS UR S19 and S22 for existing ships, and recommended standards, IACS UR S17, S18 and S20 for new ships, and the extent of possible repairs and/or reinforcements of vertically corrugated transverse watertight bulkheads on existing bulk carriers are freely available at IACS web site From 1 July 2001, bulk carriers of 20,000 DWT and above, to which the Enhanced Survey Programme (ESP) requirements apply, starting with the 3 rd Special Survey, all Special and Intermediate hull classification surveys are to be carried out by at least two exclusive surveyors. Further, one exclusive surveyor is to be on board while thickness measurements are taken to the extent necessary to control the measurement process The detailed survey requirements complying with ESP are specified in the Rules and Regulations of each IACS Member Society The ESP is based on two principal criteria: the condition of the coating and the extent of structural corrosion. Of primary importance is when a coating has been found to be in a poor condition (more than 20% breakdown of the coating or the formation of hard scale in 10 % more of the area) or when a structure has been found to be substantially corroded (i.e. a wastage between 75 % and 100 % of the allowable diminution for the structural member in question.). INTERNATIONAL ASSOCIATION OF CLASSIFICATION SOCIETIES 3 2 CLASS SURVEY REQUIREMENTS

9 BULK CARRIERS: GUIDELINES FOR SURVEY, ASSESSMENT AND REPAIR OF HULL STRUCTURE 2 CLASS SURVEY REQUIREMENTS 2.2 Annual Surveys The purpose of an Annual Survey is to confirm that the general condition of the hull is maintained at a satisfactory level As the ship ages, cargo holds are required to be subjected to more extensive overall and close-up examinations at Annual Surveys In addition, overall and close-up examinations may be required for ballast tanks as a consequence of either the coating deteriorating to a poor condition or the structure being found to be substantially corroded at previous Intermediate or Special Surveys. 2.3 Intermediate Surveys The Intermediate Survey replaces the second or third Annual Survey in each five year Special Survey cycle and requires that, in addition to the Annual Survey requirements, extended overall and close-up examinations including thickness measurements of cargo holds and ballast tanks used primarily for salt water ballast, are carried out The survey also includes re-examination and thickness measurements of any suspect areas which have substantially corroded or are known to be prone to rapid wastage Areas in ballast tanks and cargo holds found suspect at the previous Special Survey are subject to overall and close-up surveys, the extent of which becomes progressively more extensive commensurate with the age of the vessel As of 1 July 2001, for bulk carriers exceeding 15 years of age, the requirements of the Intermediate Survey are to be of the same extent as the previous Special Survey, except for pressure testing of cargo/ballast holds and ballast tanks which is not required unless deemed necessary by the attending surveyor. 2.4 Special Surveys The Special (or Renewal) Surveys of the hull structure are carried out at five-year intervals for the purpose of establishing the condition of the structure to confirm that the structural integrity is satisfactory in accordance with the Classification Requirements, and will remain fit for its intended purpose for another five-year period, subject to proper maintenance and operation of the ship and to periodical surveys carried out at the due dates The Special Survey concentrates on close-up examination in association with thickness determination and is aimed at detecting fractures, buckling, substantial corrosion and other types of structural deterioration Thickness measurements are to be carried out upon agreement with the INTERNATIONAL ASSOCIATION OF CLASSIFICATION SOCIETIES 4 2 CLASS SURVEY REQUIREMENTS

10 BULK CARRIERS: GUIDELINES FOR SURVEY, ASSESSMENT AND REPAIR OF HULL STRUCTURE 2 CLASS SURVEY REQUIREMENTS Classification Society concerned in conjunction with the Special Survey. The Special Survey may be commenced at the 4 th Annual Survey and be progressed with a view to completion by the 5 th anniversary date Deteriorated protective coating in salt water ballast spaces and structural areas showing substantial corrosion and/or considered by the surveyor to be prone to rapid wastage will be recorded for particular attention during the following survey cycle, if not repaired at the survey. 2.5 Drydocking (Bottom) Surveys A Drydocking Survey is required in conjunction with the Special Survey to examine the external underwater part of the ship and related items. Two Bottom surveys are required to be carried out during the five year period of validity of SOLAS Cargo Ship Safety Construction (SC) Certificate, and the maximum interval between any two successive Bottom Survey is not to exceed three years From 1 July 2002, for bulk carriers of 15 years of age and over, inspection of the outside of the ship s bottom is to be carried out with the ship in dry dock. For bulk carriers less than 15 years of age, alternative inspections of the ship s bottom not conducted in conjunction with the Special Survey may be carried out with the ship afloat. Inspection of the ship afloat is only to be carried out when the conditions are satisfactorily and the proper equipment and suitably qualified staff are available. 2.6 Damage and repair surveys Damage surveys are occasional surveys which are, in general, outside the programme of periodical hull surveys and are requested as a result of hull damage or other defects. It is the responsibility of the owner or owner s representative to inform the Classification Society concerned when such damage or defect could impair the structural capability or watertight integrity of the hull. The damages should be inspected and assessed by the Society s surveyors and the relevant repairs, if needed, are to be performed. In certain cases, depending on the extent, type and location of the damage, permanent repairs may be deferred to coincide with the planned periodical survey. Any damage in association with wastage over the allowable limits (including buckling, grooving, detachment or fracture), or extensive areas of wastage over the allowable limits, which affects or, in the opinion of the surveyor, will affect the vessel s structural watertight or weathertight integrity, is to be promptly and thoroughly repaired. Areas to be considered to are to include: Side shell frames, their end attachments and adjacent shell plating, deck structure and deck plating, watertight bulkheads, and hatch covers and coamings. INTERNATIONAL ASSOCIATION OF CLASSIFICATION SOCIETIES 5 2 CLASS SURVEY REQUIREMENTS

11 BULK CARRIERS: GUIDELINES FOR SURVEY, ASSESSMENT AND REPAIR OF HULL STRUCTURE 2 CLASS SURVEY REQUIREMENTS In cases of repairs intended to be carried out by riding crew during voyage, the complete procedure of the repair, including all necessary surveys, is to be submitted to and agreed upon by the Classification Society reasonably in advance IACS Unified Requirement Z 13 Voyage Repairs and Maintenance provides useful guidance for repairs to be carried out by a riding crew during a voyage For locations of survey where adequate repair facilities are not available, consideration may be given to allow the vessel to proceed directly to a repair facility. This may require discharging the cargo and/or temporary repairs for the intended voyage. A suitable condition of class will be imposed when temporary measures are accepted. INTERNATIONAL ASSOCIATION OF CLASSIFICATION SOCIETIES 6 2 CLASS SURVEY REQUIREMENTS

12 BULK CARRIERS: GUIDELINES FOR SURVEY, ASSESSMENT AND REPAIR OF HULL STRUCTURE 3 TECHNICAL BACKGROUND FOR SURVEYS 3 Technical background for surveys 3.1 General The purpose of carrying out the periodical hull surveys is to detect possible structural defects and damages and to establish the extent of any deterioration. To help achieve this and to identify key locations on the hull structure that might warrant special attention, knowledge of any historical problems of the particular ship or other ships of a similar class is to be considered if available. In addition to the periodical surveys, occasional surveys of damages and repairs are carried out. Records of typical occurrences and chosen solutions should be available in the ship's history file. 3.2 Definitions For clarity of definition and reporting of survey data, it is recommended that standard nomenclature for structural elements be adopted. Typical sections in way of cargo holds are illustrated in Figures 3 (a) and (b). These figures show the generally accepted nomenclature. The terms used in these guidelines are defined as follows. (a) Ballast Tank is a tank which is used primarily for salt water ballast. (b) Spaces are separate compartments including holds and tanks. (c) Overall examination is an examination intended to report on the overall condition of the hull structure and determine the extent of additional close-up examinations. (d) Close-up examination is an examination where the details of structural components are within the close visual examination range of the surveyors, i.e. normally within reach of hand. (e) Transverse Section includes all longitudinal members such as plating, longitudinals and girders at the deck, side, bottom and inner bottom, hopper side tanks and top wing tanks. (f) Representative Spaces are those which are expected to reflect the condition of other spaces of similar type and service and with similar corrosion protection systems. When selecting representative spaces, account should be taken of the service and repair history on board. (g) Suspect Areas are locations showing Substantial Corrosion and/or are considered by the surveyor to be prone to rapid material wastage. (h) Substantial Corrosion is an extent of corrosion such that assessment of corrosion pattern indicates a material wastage in excess of 75 per cent of allowable margins, but within acceptable limits. (i) Coating Condition is defined as follows: Good condition with only minor spot rusting. Fair condition with local breakdown at edges of stiffeners and weld connections and/or light rusting over 20 per cent or more of areas under consideration, but less than as defined for Poor condition. Poor condition with general breakdown of coating over 20 per cent or more of areas or hard scale at 10 per cent or more of INTERNATIONAL ASSOCIATION OF CLASSIFICATION SOCIETIES 7 3 TECHNICAL BACKGROUND FOR SURVEYS

13 BULK CARRIERS: GUIDELINES FOR SURVEY, ASSESSMENT AND REPAIR OF HULL STRUCTURE 3 TECHNICAL BACKGROUND FOR SURVEYS areas under consideration. (j) Transition Region is a region where discontinuity in longitudinal structure occurs, e.g. at forward bulkhead of engine room and collision bulkhead. Topside tank transverse web frame Topside tank Side shell longitudinal Deck plating Deck longitudinal Topside tank sloping plating Topside tank sloping plating longitudinal Hatch side coaming Topside tank plating vertical strake Side shell plating Bracket Side shell frame (Hold frame) Bracket Cargo hold Hopper transverse web frame Side shell longitudinal Hopper tank sloping Hopper tank sloping plating longitudinal Bottom side girder Inner bottom longitudinal Double bottom tank Bottom center girder Inner bottom plating (Tank top) Bilge plating Bilge keel Figure 3 (a) Bottom longitudinal Hopper tank Bottom shell plating Floor Keel plate Nomenclature for typical transverse section in way of cargo hold CL INTERNATIONAL ASSOCIATION OF CLASSIFICATION SOCIETIES 8 3 TECHNICAL BACKGROUND FOR SURVEYS

14 BULK CARRIERS: GUIDELINES FOR SURVEY, ASSESSMENT AND REPAIR OF HULL STRUCTURE 3 TECHNICAL BACKGROUND FOR SURVEYS Cross deck Cargo hatchway end coaming Transverse Upper stool Upper shelf plate Corrugated transverse bulkhead Cargo hatchway end transverse Cross deck structure cantilever support bracket (Note:Shedder plate may be provided at a higher position with gusset plate from a strength viewpoint) Shedder plate Gusset plate Section without diaphragm Figure 3 (b) Shedder plate Lower shelf plate Lower stool Watertight bulkhead Inner bottom plate Floor Section with diaphragm Nomenclature for typical watertight bulkhead 3.3 Structural damages and deterioration General In the context of this manual, structural damages and deterioration imply deficiencies caused by: - excessive corrosion - design faults - material defects or bad workmanship - navigation in extreme weather conditions - loading and unloading operations, water ballast exchange at sea - wear and tear - contact (with quay side, ice, touching underwater objects, etc.) but not as a direct consequence of accidents such as collisions, INTERNATIONAL ASSOCIATION OF CLASSIFICATION SOCIETIES 9 3 TECHNICAL BACKGROUND FOR SURVEYS

15 BULK CARRIERS: GUIDELINES FOR SURVEY, ASSESSMENT AND REPAIR OF HULL STRUCTURE 3 TECHNICAL BACKGROUND FOR SURVEYS groundings and fire/explosions. Deficiencies are normally recognized as: - material wastage - fractures - deformations The various types of deficiencies and where they may occur are discussed in more detail as follows: Material wastage In addition to being familiar with typical structural defects likely to be encountered during a survey, it is necessary to be aware of the various forms and possible location of corrosion that may occur to the structural members on decks, in holds, and in tanks. General corrosion appears as a non-protective, friable rust which can occur uniformly on hold or tank internal surfaces that are uncoated. The rust scale continually breaks off, exposing fresh metal to corrosive attack. Thickness loss cannot usually be judged visually until excessive loss has occurred. Failure to remove mill scale during construction of the ship can accelerate corrosion experienced in service. Severe general corrosion in all types of ships, usually characterized by heavy scale accumulation, can lead to extensive steel renewals. Grooving corrosion is often found in or beside welds, especially in the heat affected zone. The corrosion is caused by the galvanic current generated from the difference of the metallographic structure between the heat affected zone and base metal. Coating of the welds is generally less effective compared to other areas due to roughness of the surface which exacerbates the corrosion. Grooving corrosion may lead to stress concentrations and further accelerate the corrosion process. Grooving corrosion may be found in the base material where coating has been scratched or the metal itself has been mechanically damaged. Pitting corrosion is often found in the bottom plating or in horizontal surfaces, such as face plates, in ballast tanks and is normally initiated due to local breakdown of coating. Once pitting corrosion starts, it is exacerbated by the galvanic current between the pit and other metal. Erosion which is caused by the wearing effect of flowing liquid and abrasion which is caused by mechanical actions may also be responsible for material wastage Fractures In most cases fractures are found at locations where stress concentration occurs. Weld defects, flaws, and where lifting fittings used during ship construction are not properly removed are often areas where fractures are found. If fractures occur under repeated stresses which are below the yielding stress, the fractures are called fatigue fractures. In addition to the cyclic stresses induced by wave forces, fatigue fractures can also result from vibration forces introduced by main engine(s) or propeller(s), especially in the afterward part of the INTERNATIONAL ASSOCIATION OF CLASSIFICATION SOCIETIES 10 3 TECHNICAL BACKGROUND FOR SURVEYS

16 BULK CARRIERS: GUIDELINES FOR SURVEY, ASSESSMENT AND REPAIR OF HULL STRUCTURE 3 TECHNICAL BACKGROUND FOR SURVEYS hull. Fractures may not be readily visible due to lack of cleanliness, difficulty of access, poor lighting or compression of the fracture surfaces at the time of inspection. It is therefore important to identify, clean, and closely inspect potential problem areas. If the initiation points of a fracture is not apparent, the structure on the other side of the plating should be examined. Fracture initiating at latent defects in welds more commonly appears at the beginning or end of a run of welds, or rounding corners at the end of a stiffener, or at an intersection. Special attention should be paid to welds at toes of brackets, at cut-outs, and at intersections of welds. Fractures may also be initiated by undercutting the weld in way of stress concentrations. Although now less common, intermittent welding may cause problems because of the introduction of stress concentrations at the ends of each length of weld. It should be noted that fractures, particularly fatigue fractures due to repeated stresses, may lead to serious damages, e.g. a fatigue fracture in a frame may propagate into shell plating and affect the watertight integrity of the hull. In extreme weather conditions the shell fracture could extend further resulting in the loss of part of the shell plating and consequent flooding of cargo hold Deformations Deformation of structure is caused by in-plane load, out-of-plane load or combined loads. Such deformation is often identified as local deformation, i.e. deformation of panel or stiffener, or global deformation, i.e. deformation of beam, frame, girder or floor, including associated plating. If in the process of the deformation large deformation is caused due to small increase of the load, the process is called buckling. Deformations are often caused by impact loads/contact and inadvertent overloading. Damages due to bottom slamming and wave impact forces are, in general, found in the forward part of the hull, although stern seas (pooping) have resulted in damages in way of the after part of the hull. In the case of damages due to contact with other objects, special attention should be drawn to the fact that although damages to the shell plating may look small from the outboard side, in many cases the internal members are heavily damaged. Permanent buckling may arise as a result of overloading, overall reduction in thickness due to corrosion, or contact damage. Elastic buckling will not normally be directly obvious but may be detected by evidence of coating damage, stress lines or shedding of scale. Buckling damages are often found in webs of web frames or floors. In many cases, this may be attributed to corrosion of webs/floors, wide stiffener spacing or wrongly positioned lightening holes, man-holes or slots in INTERNATIONAL ASSOCIATION OF CLASSIFICATION SOCIETIES 11 3 TECHNICAL BACKGROUND FOR SURVEYS

17 BULK CARRIERS: GUIDELINES FOR SURVEY, ASSESSMENT AND REPAIR OF HULL STRUCTURE 3 TECHNICAL BACKGROUND FOR SURVEYS webs/floors. Finally, it should be noted that inadvertent overloading may cause significant damages. In general, however, major causes of damages are associated with excessive corrosion and contact damage. 3.4 Structural detail failures and repairs For examples of structural defects which have occurred in service, attention is drawn to Section 5 of these guidelines. It is suggested that surveyors and inspectors should be familiar with the contents of Section 5 before undertaking a survey Any damage to or excessive wastage of the following structures that are considered affecting the ship s Classification is to be promptly and thoroughly repaired: (a) Side shell frames, their end attachments and adjacent shell plating (b) Deck structure and deck plating between hatches (c) Watertight bulkheads (d) Hatch covers and coamings In general, where part of the structure has deteriorated to the permissible minimum thickness, then the affected area is to be cropped and renewed. Doubler plates must not be used for the compensation of wasted plate. Repair work in tanks requires careful planning in terms of accessibility If replacement of defective parts must be postponed, the following temporary measures may be acceptable at the surveyor s discretion: (a) The affected area may be sandblasted and painted in order to reduce corrosion rate. (b) Doubler may be applied over the affected area. Special consideration should be given to areas buckled under compression. (c) Stronger members may support weakened stiffeners by applying temporarily connecting elements. (d) Cement box may be applied over the affected area. A suitable condition of class should be imposed when temporary measures are accepted. 3.5 IACS Early Warning Scheme (EWS) for reporting of significant hull damage IACS has organised and set up a system to permit the collection, and dissemination amongst Member Societies of information (while excluding a ship's identity) on significant hull damages The principal purpose of the IACS Early Warning Scheme is to enable a Classification Society with experience of a specific damage to make this information available to the other societies so that action can be implemented to avoid repetition of damage to hulls where similar structural arrangements are employed. INTERNATIONAL ASSOCIATION OF CLASSIFICATION SOCIETIES 12 3 TECHNICAL BACKGROUND FOR SURVEYS

18 BULK CARRIERS: GUIDELINES FOR SURVEY, ASSESSMENT AND REPAIR OF HULL STRUCTURE 3 TECHNICAL BACKGROUND FOR SURVEYS These guidelines incorporated the experience gained from IACS EWS Scheme. INTERNATIONAL ASSOCIATION OF CLASSIFICATION SOCIETIES 13 3 TECHNICAL BACKGROUND FOR SURVEYS

19 BULK CARRIERS: GUIDELINES FOR SURVEY, ASSESSMENT AND REPAIR OF HULL STRUCTURE 4 SURVEY PLANNING, PREPARATION AND EXECUTION 4 Survey planning, preparation and execution 4.1 General The owner should be aware of the scope of the coming survey and instruct those who are responsible, such as the master or the superintendent, to prepare necessary arrangements. If there is any doubt, the Classification Society concerned should be consulted Survey execution will naturally be heavily influenced by the type of survey to be carried out. The scope of survey will have to be determined prior to the execution The surveyor should study the ship s structural arrangements and review the ship s operation and survey history and those of sister ships where possible, to identify any known potential problem areas particular to the type of ships. Sketches of typical structural elements should be prepared in advance so that any defects and/or ultrasonic thickness measurements can be recorded rapidly and accurately. 4.2 Survey Programme It is mandatory that a specific Survey Programme be worked out in advance of the Special Survey by the owner in cooperation with the Classification Society The Survey Programme should account for and comply with the requirements for close-up examinations, thickness measurements and tank testing, and take into consideration the conditions for survey, access to structures and equipment for survey The close-up survey and thickness measurement in this Survey Programme may be augmented by a Planning Document as described in 4.3 and which should be agreed with the relevant Classification Society The Survey Programme should take into account the information included in the documentation on board, as described in In developing the Survey Program, the Classification Society will advise the Owner of the maximum acceptable structural corrosion diminution levels applicable to the vessel. 4.3 Principle for Planning Document A Planning Document is intended to identify critical structural areas and to stipulate the extent and locations for close-up survey and thickness measurements with respect to sections and internal structures as well as nominated suspect areas. Minimum requirements regarding close-up surveys and thickness measurements are stipulated in IACS Unified Requirement Z The planning Document is to be worked out by the owner in cooperation INTERNATIONAL ASSOCIATION OF CLASSIFICATION SOCIETIES 14 4 SURVEY PLANNING, PREPARATION AND EXECUTION

20 BULK CARRIERS: GUIDELINES FOR SURVEY, ASSESSMENT AND REPAIR OF HULL STRUCTURE 4 SURVEY PLANNING, PREPARATION AND EXECUTION with the relevant Classification Society well in advance of the survey The basis for nomination of spaces and areas in above is a technical assessment and consideration of possible deterioration where the following elements on the particular ship are taken into account: (a) Design features such as extent of high tensile steel and local details; (b) Former history available at owner s and the relevant Classification Society s offices with respect to material wastage, fractures, deformations and repairs for the particular ship as well as similar vessels. (c) Information from same offices with respect to type of cargo, use of different spaces for cargo/ballast, protection of spaces and condition of coating, if any The Planning Document is to contain relevant information pertaining to at least the following information: (a) Main particulars (b) Main structural plans (scantling drawings), including information regarding use of high tensile steels (c) Plan of tanks/holds (d) List of tanks/holds with information on use, protection and condition of coating (e) Conditions for survey (e.g. information regarding hold and tank cleaning, gas freeing, ventilation, lighting, etc) (f) Provisions and methods for access (g) Equipment for surveys (h) Corrosion risk nomination of holds and tanks (i) Design related damages on the particular ship, and similar vessels, where available. (j) Selected holds and tanks and areas for close-up survey (k) Selected sections for thickness measurements (l) Acceptable corrosion allowance (m) Damage experience related to the ship in question 4.4 Conditions for survey The owner is to provide the necessary facilities for a safe execution of the survey Tanks and spaces are to be safe for access, i.e. gas freed (marine chemist certificate), ventilated, illuminated, etc Tanks and spaces are to be sufficiently clean and free from water, scale, dirt, oil residues, etc. and sufficient illumination is to be provided, to reveal corrosion, deformation, fractures, damages or other structural deterioration. In particular this applies to areas which are subject to thickness measurement. INTERNATIONAL ASSOCIATION OF CLASSIFICATION SOCIETIES 15 4 SURVEY PLANNING, PREPARATION AND EXECUTION

21 BULK CARRIERS: GUIDELINES FOR SURVEY, ASSESSMENT AND REPAIR OF HULL STRUCTURE 4 SURVEY PLANNING, PREPARATION AND EXECUTION 4.5 Access arrangement and safety In accordance with the intended survey, measures are to be provided to enable the hull structure to be examined and thickness measurement carried out in a safe and practical way For close-up surveys in a cargo hold and salt water ballast tanks, one or more of the following means for access, acceptable to the Surveyor, are to be provided: a) permanent staging and passages through structures; b) temporary staging, e.g. ladders and passages through structures; c) lifts and movable platforms; and d) other equivalent means In addition, particular attention should be given to the following guidance: (a) Prior to entering tanks and other closed spaces, e.g. chain lockers, void spaces, it is necessary to ensure that the oxygen content is to be tested and confirmed as safe. A responsible member of the crew should remain at the entrance to the space and if possible communication links should be established with both the bridge and engine room. Adequate lighting should be provided in addition to a hand held torch (flashlight). (b) In tanks where the structure has been coated and recently deballasted, a thin slippery film may often remain on the surfaces. Care should be taken when inspecting such spaces. (c) The removal of scale may be extremely difficult. The removal of scale by hammering may cause sheet scale to fall, and in cargo holds this may result in residues of cargo falling from above. When using a chipping or scaling hammer care should be taken to protect eyes, and where possible safety glasses should be worn. If the structure is heavily scaled then it may be necessary to request de-scaling before conducting a satisfactory visual examination. (d) Owners or their representatives have been known to request that a survey be carried out from the top of the cargo during discharging operations. For safety reason, surveys must not to be carried out during discharging operations in the hold. (e) In bulk carriers fitted with vertical ballast trunks connecting the topside and lower hopper tanks, the trunks and associated hull structure are normally surveyed in conjunction with the tanks. Space within the trucks is very limited and access is by ladder or individual rungs which can become heavily corroded and in some cases detached or missing. Care needs to be taken when descending these trunks. (f) When entering a cargo hold or tank the bulkhead vertical ladders should be examined prior to descending to ensure that they are in good condition and rungs are not missing or loose. If holds are being entered when the hatch covers are in the closed position, then adequate lighting should be arranged in the holds. One person at a INTERNATIONAL ASSOCIATION OF CLASSIFICATION SOCIETIES 16 4 SURVEY PLANNING, PREPARATION AND EXECUTION

22 BULK CARRIERS: GUIDELINES FOR SURVEY, ASSESSMENT AND REPAIR OF HULL STRUCTURE 4 SURVEY PLANNING, PREPARATION AND EXECUTION time should descend or ascend the ladder. (g) Sloping ( Australian Style ) bulkhead ladders are prone to cargo handling damage and it is not uncommon to find platforms and ladders in poor condition with rails and stanchions missing or loose. (h) If a portable ladder is used for survey purposes, the ladder should be in good condition and fitted with adjustable feet, to prevent it from slipping. Two crew members should be in attendance in order that the base of the ladder is adequately supported during use. The remains of cargo, in particular fine dust, on the tank top should be brushed away as this can increase the possibility of the ladder feet slipping. (i) If an extending/articulated ladder (frame walk) is used to enable the examination of upper portions of cargo hold structure, the ladder should incorporate a hydraulic locking system and a built in safety harness. Regular maintenance and inspection of the ladder should be confirmed prior to its use. (j) If a hydraulic arm vehicles ( Cherry Picker ) is used to enable the examination of the upper parts of the cargo hold structure, the vehicle should be operated by qualified personnel and there should be evidence that the vehicle has been properly maintained. The standing platform should be fitted with a safety harness. For those vehicles equipped with a self leveling platform, care should be taken that the locking device is engaged after completion of maneuvering to ensure that the platform is fixed. (k) Staging is the most common means of access provided especially where repairs or renewals are being carried out. It should always be correctly supported and fitted with handrails. Planks should be free from splits and lashed down. Staging erected hastily by inexperienced personnel should be avoided. In topside and lower hopper tanks it may be necessary to arrange staging to provide close-up examination of the upper parts of the tank particularly the transverse web frames, especially where protective coatings have broken down or have not been applied. (l) In double bottom tanks there will often be a build up of mud on the bottom of the tank and this should be removed, in particular in way of tank boundaries, suction and sounding pipes, to enable a clear assessment of the structural condition. 4.6 Personal equipment The following protective clothing and equipment to be worn as applicable during the surveys: (a) Working clothes: Working clothes should be of a low flammability type and be easily visible. (b) Head protection: Hard hat (metal hats are not allowed) shall always be worn outside office building/unit accommodations. (c) Hand and arm protection: Various types of gloves are available for use, and these should be used during all types of surveys. Rubber/plastic gloves may be necessary when working in cargo holds. INTERNATIONAL ASSOCIATION OF CLASSIFICATION SOCIETIES 17 4 SURVEY PLANNING, PREPARATION AND EXECUTION

23 BULK CARRIERS: GUIDELINES FOR SURVEY, ASSESSMENT AND REPAIR OF HULL STRUCTURE 4 SURVEY PLANNING, PREPARATION AND EXECUTION (d) Foot protection: Safety shoes or boots with steel toe caps and non slip soles shall always be worn outside office buildings/unit accommodations. Special footwear may be necessary on slippery surfaces or in areas with chemical residues. (e) Ear protection: Ear muffs or ear plugs are available and should be used when working in noisy areas. As a general rule, you need ear protection if you have to shout to make yourself understood by someone standing close to you. (f) Eye protection: Goggles should always be used when there is danger of getting solid particles or dust into the eyes. Protection against welding arc flashes and ultraviolet light should also be considered. (g) Breathing protection: Dust masks shall be used for protection against the breathing of harmful dusts, paint spraying and sand blasting. Gas masks and filters should be used by personnel working for short periods in an atmosphere polluted by gases or vapour. (Self-contained breathing apparatus: Surveyors shall not enter spaces where such equipment is necessary due to unsafe atmosphere. Only those who are specially trained and familiar with such equipment should use it and only in case of emergency). (h) Lifejacket: Recommended used when embarking/disembarking ships offshore, from/to pilot boat The following survey equipment is to be used as applicable during the surveys: (a) Torches: Torches (Flashlights) approved by a competent authority for use in a flammable atmosphere shall be used in gas dangerous areas. High intensity beam type is recommended for in-tank inspections. Torches are recommended to be fitted with suitable straps so that both hands may be free. (b) Hammer: In addition to its normal purposes the hammer is recommended for use during surveys inside units, tanks etc. as it may be most useful for the purpose of giving distress signal in case of emergency. (c) Oxygen analyser/multigas detector: For verification of acceptable atmosphere prior to tank entry, pocket size instruments which give audible alarm when unacceptable limits are reached are recommended. Such equipment shall have been approved by national authorities. (d) Safety belts and lines: Safety belts and lines should be worn where high risk of falling down from more than 3 meters is present. (e) Radiation meter: For the purpose of detection of ionizing radiation (X or gamma rays) caused by radiographic examination, radiation meter of the type which gives audible alarm upon detection of radiation is recommended. 4.7 Thickness measurement and fracture detection Thickness measurement is to comply with the requirements of the Classification Society concerned. Thickness measurement should be INTERNATIONAL ASSOCIATION OF CLASSIFICATION SOCIETIES 18 4 SURVEY PLANNING, PREPARATION AND EXECUTION

24 BULK CARRIERS: GUIDELINES FOR SURVEY, ASSESSMENT AND REPAIR OF HULL STRUCTURE 4 SURVEY PLANNING, PREPARATION AND EXECUTION carried out at points that adequately represent the nature and extent of any corrosion or wastage of the respective structure (plate, web, etc.) Thickness measurement is normally carried out by means of ultrasonic test equipment. The accuracy of the equipment is to be proven as required The required thickness measurements, if not carried out by the class society itself, are to be carried out by a qualified company certified by the relevant classification society, and are to be witnessed by a surveyor on board to the extent necessary to control the process. The report is to be verified by the surveyor in charge The thickness measurement company should be part of the survey planning meeting to be held prior to the survey One or more of the following fracture detection procedures may be required if deemed necessary and should be operated by experienced qualified technicians: (a) radiographic equipment (b) ultrasonic equipment (c) magnetic particle equipment (d) dye penetrant 4.8 Survey at sea or at anchorage Voyage surveys may be accepted provided the survey party is given the necessary assistance from the shipboard personnel. The necessary precautions and procedures for carrying out the survey are to be in accordance with 4.1 to 4.7 inclusive. Ballasting system must be secured at all times during tank surveys A communication system is to be arranged between the survey party in the spaces under examination and the responsible officer on deck. 4.9 Documentation on board The following documentation is to be placed on board and maintained and updated by the owner for the life of ship in order to be readily available for the survey party Survey Report File: This file includes Reports of Structural Surveys, Executive Summary and Thickness Measurement Report Supporting Documents: The following additional documentation is to be placed on board, including any other information that will assist in identifying Suspect Areas requiring examination. (a) Main structural plans of cargo holds and ballast tanks (b) Previous repair history (c) Cargo and ballast history (d) Inspection and action taken by ship's personnel with reference to: - structural deterioration in general INTERNATIONAL ASSOCIATION OF CLASSIFICATION SOCIETIES 19 4 SURVEY PLANNING, PREPARATION AND EXECUTION

25 BULK CARRIERS: GUIDELINES FOR SURVEY, ASSESSMENT AND REPAIR OF HULL STRUCTURE 4 SURVEY PLANNING, PREPARATION AND EXECUTION - leakages in bulkheads and piping - condition of coating or corrosion protection, if any (e) Survey Planning Document according to principles given in Prior to inspection, the completeness of the documentation onboard, and its contents as a basis for the survey should be examined. INTERNATIONAL ASSOCIATION OF CLASSIFICATION SOCIETIES 20 4 SURVEY PLANNING, PREPARATION AND EXECUTION

26 BULK CARRIERS: GUIDELINES FOR SURVEY, ASSESSMENT AND REPAIR OF HULL STRUCTURE 5 STRUCTURAL DETAIL FAILURES AND REPAIRS 5 Structural detail failures and repairs 5.1 General The catalogue of structural detail failures and repairs contained in this section of the Guidelines collates data supplied by the IACS Member Societies and is intended to provide guidance when considering similar cases of damage and failure. The proposed repairs reflect the experience of the surveyors of the Member Societies, but it is realized that other satisfactory alternative methods of repair may be available. However, in each case the repairs are to be completed to the satisfaction of the Classification Society surveyor concerned. 5.2 Catalogue of structural detail failures and repairs The catalogue has been sub-divided into parts and areas to be given particular attention during the surveys: Part 1 Cargo hold region Area 1 Deck structure Area 2 Topside tank structure Area 3 Side structure Area 4 Transverse bulkheads including stool structure Area 5 Double bottom including hopper tank structure Part 2 Fore and aft end regions Area 1 Fore end structure Area 2 Aft end structure Area 3 Stern frame, rudder arrangement and propeller shaft support Part 3 Machinery and accommodation spaces Area 1 Engine room structure Area 2 Accommodation structure INTERNATIONAL ASSOCIATION OF CLASSIFICATION SOCIETIES 21 5 STRUCTURAL DETAIL FAILURES AND REPAIRS

27 Part 1 Cargo hold region Contents Area 1 Area 2 Area 3 Area 4 Area 5 Deck structure Topside tank structure Side structure Transverse bulkheads including stool structure Double bottom including hopper tank structure INTERNATIONAL ASSOCIATION OF CLASSIFICATION SOCIETIES PART 1 22

28 Area 1 Deck structure Contents 1 General 2 What to look for - On-deck inspection 2.1 Material wastage 2.2 Deformations 2.3 Fractures 3 What to look for - Under-deck inspection 3.1 Material wastage 3.2 Deformations 3.3 Fractures 4 General comments on repair 4.1 Material wastage 4.2 Deformations 4.3 Fractures 4.4 Miscellaneous Figures and/or Photographs - Area 1 No. Photograph 1 Title Heavy corrosion of hatch coaming and topside tank plating vertical strake Examples of structural detail failures and repairs - Area 1 Example No. Title 1 Fractures at main cargo hatch corner 2-a Fracture of welded seam between thick plate and thin plate at cross deck 2-b Plate buckling in thin plate near thick plate at cross deck 2-c Overall buckling of cross deck plating 3-a Fractures in the web or in the deck at the toes of the longitudinal hatch coaming termination bracket 3-b Fractures in the web or in the deck at the toes of the longitudinal hatch coaming termination bracket 4 Fractures in deck plating initiated from weld of access manhole 5 Deformed and fractured deck plating around tug bitt 6 Fractures around cut-outs in cross deck girder 7-a Buckling of hatch coaming and hatch end beam 7-b Fractures in hatch end beam at knuckle joint INTERNATIONAL ASSOCIATION OF CLASSIFICATION SOCIETIES AREA 1 23